1. Field of the Invention
The present invention relates to a stator for an electrical machine including a plurality of stator coils arranged on a stator yoke and an interconnection arrangement arranged on one end face of the stator yoke having connecting conductors which are electrically insulated from one another and arranged concentrically with respect to one another. Each connecting conductor has a different diameter. The connecting conductors have connections for connection to the ends of the stator coils and for connection to the electrical machine. The present invention also relates to a method for producing such a stator.
2. Description of the Related Art
Stators for electrical machines generally have a plurality of stator teeth on which stator coils are wound. The coils are associated with individual phases of electrical power. The coils associated with a common phase are interconnected. In a three-phase machine the stator has three phases. Each of the phases have current applied to them separated by phase angles of 120xc2x0. The current input and the current output from the individual coils are passed out of the electrical machine at one stator end.
In known stators, the individual coils are interconnected by hand. In doing so, the individual coil ends of each coil were routed to the respective connections for connection to the electrical machine and electrically connected there. However, this type of interconnection has a number of disadvantages. For example, the separate interconnection of the individual coils to the corresponding connections for connection to the electrical machine results in thick cable harnesses which add to the space requirements of the electric machine. Space requirements are becoming more important in many applications. For example, a stator of the above-described type intended to be used in a vehicle is limited to the amount of area available in the engine compartment. Accordingly, efforts are being made to design individual components used in the engine compartment to be as small and space-saving as possible.
Furthermore, the known method of connecting individual coils requires that the individual wires of the coil ends be carefully insulated from one another. This requirement necessitates the use of additional insulation material and thus leads to a further increase in the required physical space. Finally, there is also a risk that faults can occur when the coil ends are being associated and correspondingly interconnected. Owing to the large number of wires, it is difficult to determine when a coil has been incorrectly connected, and when this situation occurs, which of the coils has been incorrectly connected. If a short circuit occurs in the interconnection arrangement, it is difficult and time consuming to locate the defect point.
Furthermore, the known interconnection arrangement is also highly costly, since the interconnection process must be carried out by hand. Automation of the process for production of such interconnection arrangements is impossible, so that the known interconnection arrangements are not suitable for large-scale production.
A known stator for electrical machines is disclosed in the preamble of claim 1 in the German reference DE 195 44 830 A1. In this stator, there is no individual interconnection of the respective coils to the connections for connection to the electrical machine. Instead, connecting conductors designed as ring conductors are proposed which are electrically insulated from one another and are arranged concentrically in an insulating slot structure and with a different diameter. The individual coil ends are connected via projections to the connecting conductors, with the projections projecting out of the interconnection arrangement body. This known stator avoids the complex individual interconnection of the individual coils, but this stator also has a number of disadvantages.
For example, this stator as well requires a relatively large amount of area because the interconnection arrangement is arranged in front of the coils in the axial direction. Furthermore, the projections provided for connection of the coil ends to the connecting conductors are aligned in a rigid manner at right angles to the connecting conductors which increases the area requirement for the interconnection arrangement and thus for the entire stator.
Another electrical machine having a stator provided with coils and connecting elements in the form of a ring provided for interconnection of the coils is disclosed in German reference DE 196 47 559 A1. These connecting elements designed in the form of a ring are arranged radially or axially adjacent and are electrically insulated from one another. The connection of the individual coil ends to the connecting conductors is made via openings formed in the conductors. The coil ends are passed through the openings and are then attached. This solution also still requires a relatively large amount of area, since the interconnection arrangement is once again arranged in front of the coils in the axial direction.
It is an object of the present invention to provide a stator for an electrical machine that avoids the problems of the prior art. More specifically, it is an object of the present invention to provide a stator for an electrical machine, in which the production of the individual components and the process of interconnecting the coils may be automated and carried out cost-effectively. Furthermore, the stator is intended to be designed to be particularly space-saving. In particular, the losses which occur in the stator are also intended to be minimized. Furthermore, an appropriately improved method for producing a stator is intended to be provided.
The object of the present invention is achieved by a stator comprising an interconnection arrangement arranged radially inside an area bounded by the stator coils. The connections for the ends of the stator coils comprise connection projections designed such that they project outward to attach the stator coil ends at an angle to the respective connecting conductor. Furthermore, a plurality of cutouts are provided in the interconnection arrangement for the connection projections, into which cutouts the connection projections may be bent or are bent.
The stator according to the present invention allows automatic production of the interconnection arrangement in a simple and cost-effective manner and allows automatic interconnection of the individual coils. At the same time, the area required for the interconnection arrangement, and thus for the entire stator, is considerably reduced compared to the prior art.
A fundamental idea of the present invention is that the stator coils are first fitted to the stator yoke. The connecting conductors are then introduced into the area which is bounded by the stator coils. The connecting conductors have a diameter which is smaller than the diameter of the surface bounded by the coils. Accordingly, the individual connecting conductors are no longer located axially in front of the coils, or their end windings, as has been described with respect to the known solutions. In fact, the connecting conductors are now arranged coaxially with respect to the stator coils, underneath or inside them. The individual connecting conductors preferably have a width which is matched to the end windings of the individual coils, so that the connecting conductors do not project beyond the coils, either in the axial or in the radial direction. The stator thus has a width which is governed only by the coil geometry.
The ends of each of the coils are attached to the connection projections on the connecting conductors. To accommodate this connection, the connection projections are designed such that they initially project at an angle, preferably at an angle of 90xc2x0, to the respective connecting conductor. This enables a simple connection of the coil ends to the connection projections.
Once the coil ends have been attached, the connection projections are bent into appropriate cutouts provided in the connecting conductors. In consequence, the axial space occupied by the projecting connection projections is not required after the coil ends have been connected to the connecting conductors.
In principle, the present invention is not limited to specific connecting conductor cross sections. However, it has been found to be particularly advantageous to design the individual connecting conductors with a quadrilateral conductor cross section. This design allows the individual connecting conductors to be pushed into one another in a simple and accurate manner.
Depending on the current conducting requirement, the connections for connection to the electrical machine may be in the form of plugs, sleeves, plug pins, cable lugs or other electrical connections. However, the invention is not limited to the cited examples of electrical connections, so that other embodiments for the electrical connections are also conceivable and possible.
The individual components of the stator according to the present invention may be produced in a simple and cost-effective manner. The individual coils may then be interconnected by an automated process. Furthermore, the particularly advantageous arrangement of the interconnection arrangement inside the area bounded by the stator coils allows the stator to be configured in a particularly space-saving manner. Finally, the configuration of the stator according to the invention, in particular the choice of the cross sections for the connecting conductors, also minimizes any possible resistive heat losses.
The stator may be used for every possible form of electrical machine. Electrical machines in which the stator of the present invention may be installed include, but are not limited to, for example, synchronous machines and especially synchronous machines with permanent-magnet excitation. One machine which is particularly worthy of mention is, for example, the starter generator for vehicles. This is an electrical machine whose rotors are borne via the crankshaft bearing of the internal combustion engine. The starter generator is used not only for starting and stopping the internal combustion engine, but may also carry out various functions during operation of the engine, such as braking functions, booster functions, battery management, active oscillation damping, synchronization of the internal combustion engine, and other functions. The starter generator may comprise an external-rotor synchronous machine and may be connected to the engine block of the internal combustion engine via a stator support as a supporting element.
The connection projections are advantageously arranged in the region of the stator coil ends. This allows the distances between the connection projections and the stator coil ends to be particularly short. This arrangement also prevents faults in the interconnection of the coils of one phase. The coils are interconnected in a clear manner, so that any possible defect in the interconnection of the coils may be easily identified.
An insulating layer is preferably provided between each of the connecting conductors. The insulating layer may advantageously be very thin and may, for example, comprise insulating paper, insulating film or other insulating material. The insulating layer may be loosely arranged between the individual connecting conductors, bonded to the connecting conductors, or fitted between the connecting conductors in some other way. The invention is not limited to specific embodiment forms of the insulating layer or to specific insulating materials.
In a further refinement, the interconnection arrangement may be arranged above an insulating layer on the stator yoke. This insulating layer may, for example, comprise an insulating disk or the like.
The stator coil ends are advantageously connected to the connection projections via a jointed connection and/or a mechanical connection. For example, the coil ends may be soldered to the connection projections using, for example, a soldering or brazing process. It is also conceivable for the coil ends to be welded to the connection projections. Preferred welding processes include resistance welding, laser welding, or ultrasound welding. However, any other welding may also be used. The mechanical connections used may be, for example, crimped connections. However any other mechanical connection for effecting the connection may also be used.
The connections for connection to the electrical machine are preferably each passed from the radial inside of the stator yoke between two adjacent stator coils to the radial outer side of the stator yoke. To do this, the connections may be passed radially outward through the gaps that exist between two adjacent stator coils, leading to a further reduction in the axial physical space.
Each of the connecting conductors are preferably produced from a strip material. This allows the connecting conductors to be produced by an automated process which is particularly easy and cost-effective. The individual connecting conductors may be produced from any suitably conductive material such as copper and may be rolled by a suitable rolling process and wound to form coils. The connection projections, and the cutouts required in the connecting conductors, may be incorporated in the connecting conductors by any suitable method such as, for example, stamping methods, cutting methods or other machining processes.
In a further refinement, one or more of the connecting conductors may have one or more cutouts for the connections to pass through for connection to the electrical machine. Such cutouts are physically necessary since the connecting conductors are arranged radially one above the other, and electrically necessary to prevent electrical contact between the connections and the respective adjacent connecting conductors.
The interconnection arrangement may preferably have three connecting conductors for a three-phase machine.
The number of connecting conductors depends on the application and the embodiment of the stator. In the same way, the number of stator coils used may vary for different stator application areas. Since each of the stator coils is connected via two connection projections to appropriate connecting conductors, the number of connection projections and the number of cutouts for the connection projections may be varied as required when the number of stator coils varies.
The connecting conductors may advantageously be designed in the form of a ring or in the form of a ring segment. This allows the connecting conductors to be matched particularly advantageously to the geometry of the stator and to the arrangement geometry of the stator coils.
According to one preferred embodiment of the stator according to the invention, the connecting conductors are designed as closed ring structures. The end regions of the ring structures are designed as respective connections for connection to the electrical machine. In this embodiment, the individual connecting conductors are produced first of all as strip material and then cut to the required length. After this, the connecting conductors (which are initially in the form of flat strips) are bent to form ring structures with the required diameter. The end regions of the ring segments may then be bent at a desired angle, for example at right angles to the connecting conductor, and thus form a respective connection for connection to the electrical machine. Those end regions which are designed as a connection may advantageously be connected to one another using a suitable joining process, for example, which increases the robustness of the annular connecting conductor.
According to another embodiment of the invention, the connecting conductors may be designed as open ring structures, in which case the individual ring structures may each have a different length. In this embodiment, one of the end regions of a respective ring structure may be designed as a connection for connection to the electrical machine. Such a refinement of the individual connecting elements further simplifies the production. The configuration as an open ring structure and the fact that the individual connecting conductors have a different length eliminates the need for forming cutouts for the connections to pass through.
In yet another refinement to the invention, the connecting conductors may be designed as closed rings, with the connections for connection to the electrical machine each being arranged on the rings. The connections may each be arranged in an appropriate cutout in the connecting conductors. In this embodiment, the respective connections are not required to be formed as specially designed end regions of the connecting conductors. In fact, individual connecting conductors may be produced first of all in the form of closed rings, with the connections then being attached to the connecting conductors. The connections are advantageously once again arranged in appropriately designed cutouts on the connecting conductors. This once again makes it possible for the connections to be passed between the respective adjacent connecting conductors without any possibility of electrical contact between the connections and the respective adjacent connecting conductors.
Each of the stator coils advantageously comprises an end winding and an insulating body and is produced using an individual tooth winding technique. This production technique allows the coils to be wound automatically on the respective teeth. After winding, the individual coil produced in this way is then connected to the stator yoke.
The interconnection arrangement may advantageously be arranged via a jointed connection and/or a mechanical connection on the stator yoke or on the insulating body of the stator coils. This arrangement of the interconnection arrangement must be adopted owing to the natural weight of the interconnection arrangement and the oscillations which occur in the electrical machine. The fixing of the interconnection arrangement is necessary since, otherwise, the coil ends could tear off or be damaged. The interconnection arrangement, and the connecting conductors of the circuit arrangement, may advantageously be arranged on the stator yoke or on the insulating bodies of the stator coils via a clip or by some other type of mechanical attachment such as, for example, screwing, riveting, welding. The connection of the interconnection arrangement to the stator yoke and/or the insulating bodies of the stator coils is not limited to the above listed connections and may be effected by any mechanical connection.
In a further refinement, the stator may be impregnated. This results in a particularly solid structure. The stator, and the individual components of the stator, may, for example, be encased by a high-temperature cast resin, which is electrically insulating and assists thermal conduction to dissipate the heat losses released in the stator coils.
According to the present invention, a method for producing a stator according to the present invention, as described above, is distinguished according to the present invention by the following steps:
a) fitting the stator coils to the stator yoke;
b) introducing the interconnection arrangement which comprises a plurality of connecting conductors which are insulated from one another into an area which is bounded by the stator coils, so that the interconnection arrangement does not project either in the axial direction or in the radial direction beyond the end windings of the stator coils;
c) attaching the stator coil ends to the connection projections of the plural connecting conductors; and
d) bending of the connection projections into the cutouts provided for receiving the connecting conductors.
The method according to the present invention allows simple, cost-effective interconnection of the individual stator coils to the connection conductors which may be automated. The advantages, influences, effects and method of operation of the method according to the invention is described above in the discussion of the stator according to the present invention.
The stator coils are advantageously produced using the individual -tooth winding technique.
In a further refinement, the connecting conductors of the interconnection arrangement are initially produced as strip material and are then cut to the desired length.
In a further refinement, the stator coil ends are attached to the connection projections via a jointed connection and/or a mechanical connection.
The connections for connection of the connection conductors to the electrical machine are preferably each passed through between two adjacent stator coils.
The stator may advantageously subsequently be impregnated.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.